Rod Coupling System and Devices and Methods of Making and Using the Same

ABSTRACT

Provided are rod coupler devices, systems, kits and methods, which include at least one saddle having a concave configuration that either abuts a bone fastener and/or a locking cap and is shaped so as to contact the rod in two or more lines of contact, which reduces pressure on the rod, and therefore permits use of a rod having various materials, such as PEEK, without significant deformation of the rod. Also provided is the saddle itself and integrated locking caps that include a saddle, the locking cap and a set screw. Also provided are elongate rods having advantageous shapes, configurations, and/or compositions for rod coupler devices, systems and methods. Further provided are screw and cap devices and systems that themselves include a concave configuration so as to contact a rod in two or more lines of contact, which reduces pressure on the rod.

TECHNICAL FIELD

The present invention relates to orthopedic rod coupler systems,devices, kits, and methods. Examples include a saddle configured toattach to either a bone fastener or a locking cap of the rod couplersystem and having a concave portion configured to increase surface areaof contact with a rod so as to reduce pressure on the rod, particularlywhen the rod is tightened within the rod coupler system. Other examplesinclude bone fasteners or caps that themselves are configured to have aconcave portion, which increases surface area of contact with a rod. Thereduced pressure on the rod enables use of rods of various compositions,including Polyether ether ketone (“PEEK”), without deformation of therod. The invention also relates to elongate rods having advantageousshapes, configurations, and/or compositions for rod coupler devices,systems and methods.

BACKGROUND

Many types of spinal irregularities can cause pain, limit range ofmotion, or injure the nervous system within the spinal column. Theseirregularities can result from, without limitation, trauma, tumor, discdegeneration, and disease. Often, these irregularities are treated byimmobilizing a portion of the spine. This treatment typically involvesaffixing a plurality of bone fasteners such as screws and/or hooks toone or more vertebrae and connecting the screws or hooks to an elongaterod that generally extends in the direction of the axis of the spine.

Treatment for these spinal irregularities often involves using a systemof pedicle screws and rods to attain stability between spinal segments.Such systems may provide support or stability to the spinal bonestructure, which may promote healing of the bone structures and/orotherwise maintain alignment and spacing of the spinal bone structures.Instability in the spine can create stress and strain on neurologicalelements, such as the spinal cord and nerve roots. In order to correctthis, implants of certain stiffness can be implanted to restore thecorrect alignment and portion of the vertebral bodies. In many cases, ananchoring member such as a pedicle screw along with a vertical solidmember can help restore spinal elements to a pain free situation, or atleast may help reduce pain or prevent further injury to the spine.

The screw systems can include coupling members that attach pediclescrews to rods. There is a need for improved coupling members toaccommodate different types of rods.

SUMMARY

Existing bone screws systems may be used to secure a rod between twosurfaces. For example, systems can include a coupling member thatreceives a locking cap, whereby a rod is secured between a flat surfaceof the coupling member and a flat surface of the locking cap. Thiscreates a small area of contact along the line of tangency on both sidesof the rod, and thus puts a large amount of pressure on the rod. Whenused with a non-titanium rod, such as a PEEK rod, this configurationplastically deforms the rod. PEEK is a very notch sensitive material,and this deformation greatly reduces the mechanical strength of the rod.

The present inventions generally solve the problem of being able to usePEEK rods with pedicle screws and rod coupler systems (includingexisting pedicle screws and rod coupler systems). Examples of thecurrent devices, systems and methods involve a specially designed saddleinsert, locking cap, and/or unique rod shapes, which increase thesurface area contact with rods, such as rods including PEEK, to reducenotching of the rod. The present inventions may also include a new bonefastener, such as a screw, with the specialized geometry of the insert,e.g, a concave portion incorporated into the screw itself. The bonefastener can optionally be used e.g., in conjunction with thespecialized locking cap to increase surface area contact on multiplesides of the rod.

In non-limiting example embodiments, rod coupler systems may include acoupling body having a bone fastener disposed therethrough, and a saddlehaving a first side of the saddle abutting the bone fastener within thecoupling body, and a second side of the saddle opposite the first side,having a concave portion configured to abut an elongate rod along atleast two lines of contact between the saddle and the rod.

According to other example embodiments, a rod coupler system is providedwhich includes a coupling body having a bone fastener disposedtherethrough, a locking cap adapted for attachment to the coupling body,and a saddle having a first side of the saddle abutting the locking cap,and a second side of the saddle opposite the first side, the second sidehaving a concave portion configured to abut an elongate rod along atleast two lines of contact between the saddle and the elongate rod.

Also provided are saddles that include a first side configured to beattached to a bone fastener or to a locking cap for a coupling body; anda second side opposite the first side of the saddle, the second sidehaving a concave portion configured to abut an elongate rod along atleast two lines of contact between the saddle and the elongate rod.

Also provided are integrated locking caps that include a locking capadapted for attachment to a coupling body, and a saddle having a firstside of said saddle removably attached to the locking cap, a second sideof the saddle opposite the first side, the second side having a concaveportion configured to receive and abut an elongate rod along at leasttwo lines of contact between the saddle and the elongate rod, and a setscrew disposed through the locking cap.

Further example embodiments include polyaxial screws and locking capshaving a concave portion configured to abut an elongate rod along atleast two lines of contact between the polyaxial screw and/or thelocking cap and the rod.

Other example embodiments include kits that include one or morecomponents of the present devices and systems. For example, kits mayinclude a coupling body and a saddle, or they may include a locking capand a saddle. Kits may include many other possible components as well.At least two components may be preassembled together within the kit.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages, which form the subject of the claimsof the invention, will be described herein. It should be appreciated bythose skilled in the art that any specific embodiment disclosed hereinmay be readily utilized as a basis for modifying or designing otherstructures for carrying out the same purposes of the present invention.It should also be realized by those skilled in the art that suchequivalent constructions do not depart from the spirit and scope of theinvention as set forth in the appended claims. The novel features whichare believed to be characteristic of the invention, both as to itsorganization and method of operation, together with further objects andadvantages will be better understood from the following description whenconsidered in connection with the accompanying figures. It is to beexpressly understood, however, that any description, figure, example,etc. is provided for the purpose of illustration and description onlyand is by no means intended to define the limits the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting example embodiments described herein, with reference to thefollowing accompanying Figures.

FIG. 1 depicts a perspective view of a saddle that may be used inexample embodiments of the present devices and systems.

FIG. 2 depicts a perspective view of a pedicle screw having the saddleof FIG. 1 inserted therein in accordance with embodiments of the presentdevices and systems.

FIG. 3 depicts a front view of the pedicle screw of FIG. 2, having a rodinserted therein.

FIG. 4 depicts an exploded view of an integrated locking cap assemblyaccording to example embodiments of the present devices and systems.

FIG. 5 depicts a perspective view of an assembled integrated locking capassembly having the components depicted in FIG. 4.

FIG. 6 depicts a cross sectional view of the integrated locking capassembly of FIG. 5, in which the saddle is not engaged with a lockingcap.

FIG. 7 depicts a cross sectional view of the integrated locking capassembly of FIG. 6, in which the saddle is turned 90 degrees to engagethe saddle with the locking cap.

FIG. 8 depicts a perspective view of the integrated locking cap assemblyof FIG. 7, in which the saddle is engaged with the locking cap.

FIG. 9 depicts a perspective view of a pedicle screw assembly having arod inserted therein and the integrated locking cap assembly of FIG. 8inserted over the rod.

FIG. 10 depicts a perspective view of the pedicle screw assembly havinga rod inserted therein and the integrated locking cap assembly of FIG. 8inserted over the rod, in which the cap is rotated to lock the cap ontothe screw head.

FIG. 11 depicts a cross sectional front view of the assembly of FIG. 10in which the integrated locking cap depicted e.g., in FIG. 8 isconfigured in a pedicle screw assembly over an elongate rod.

FIG. 12 depicts a perspective view of polyaxial screw in which the headis configured to have a concave portion for receiving a rod inaccordance with non-limiting example embodiments.

FIG. 13 depicts a perspective view of polyaxial screw depicted in FIG.12 having a locking cap in accordance with non-limiting exampleembodiments.

FIG. 14 depicts a front view of a saddle which may be used in accordancewith non-limiting example embodiments, which has a smaller radius thanthe radius of a rod to be inserted therein.

FIG. 15 depicts non-limiting example embodiments of an obrand rod whichmay be used in accordance with the present invention.

FIG. 16 depicts a non-limiting example embodiment of a composite rodthat may be used in accordance with the present invention.

FIG. 17 depicts example PEEK rods that may be used in accordance withthe present invention, which offer various levels of stiffness.

FIG. 18 depicts example PEEK rods that may be used in accordance withthe present invention, which also offer various levels of stiffness anddepicts topping off.

FIG. 19 depicts examples of barreled rods in accordance withnon-limiting example embodiments.

FIG. 20 depicts a posted screw system that may be used in accordancewith non-limiting example embodiments.

FIG. 21 depicts a collet system that may be used in accordance with thenon-limiting example embodiments.

FIG. 22 depicts a cross sectional view of an example rod having flatsthat may be used in accordance with the present invention.

FIG. 23 depicts front (A) and side (B) cross sectional views of a dimpleinterface of a saddle with a rod in accordance with non-limiting exampleembodiments.

FIG. 24 depicts a perspective exploded view of an integratedsaddle-locking cap in accordance with non-limiting example embodiments.

FIG. 25 depicts a side view of the integrated saddle-locking cap of FIG.24, fully assembled.

FIG. 26 depicts a side, cross-sectional view of a fully assembledsaddle-locking cap design showing a tongue and groove.

FIG. 27 depicts a front view of a saddle-locking cap design insertedinto standard screw head.

FIG. 28 depicts a front view of a saddle-locking cap design insertedinto a standard screw head, which has been rotated 90 degrees and lockedinto place.

FIG. 29 depicts a front view of a saddle-locking cap design, in which aset screw has been tightened and the saddle abuts the rod, locking therod.

DETAILED DESCRIPTION

The aspects, advantages and/or other features of example embodiments ofthe invention will become apparent in view of the following detaileddescription, taken in conjunction with the accompanying drawings. Indescribing example embodiments, specific terminology is employed for thesake of clarity. However, the embodiments are not intended to be limitedto this specific terminology. It should be apparent to those skilled inthe art that the described embodiments of the present invention aremerely exemplary and illustrative and not limiting. Numerous embodimentsof modifications thereof are contemplated as falling within the scope ofthe present invention and equivalents thereto. It is to be understoodthat each specific element includes all technical equivalents thatoperate in a similar manner to accomplish a similar purpose.

Unless otherwise noted, technical terms are used according toconventional usage.

As used herein, “a” or “an” may mean one or more. As used herein,“another” may mean at least a second or more. Furthermore, unlessotherwise required by context, singular terms include pluralities andplural terms include the singular.

As indicated above, the present inventions generally solve the problemof being able to use PEEK rods, or rods of other materials, with pediclescrews and rod coupler systems by increasing contact area with the rodsand thereby reducing pressure on the rods. In some embodiments, apolyaxial pedicle screw made of titanium is provided as part of thecoupling system, which is highly resistant to corrosion and fatigue, andis MRI compatible. The screw is threaded and the head is mobile—itswivels helping to defray vertebral stress. Like other screws, polyaxialscrews come in many sizes. In some embodiments, a polyaxial pediclescrew length ranges from 30 mm to 60 mm (up to 2½ inches). In someembodiments, the diameter ranges from 5.0 mm to 8.5 mm (up to ¼ inch).Polyaxial pedicle screws are used to correct deformity, and/or treattrauma. Similar to other bone screws, pedicle screws may be used ininstrumentation procedures to affix rods and plates to the spine. Thescrews may also be used to immobilize part of the spine to assist fusionby holding bony structures together. However, when such screws are usedon rod coupling systems, the rod needs to be equally strong, so thatplastic deformation of the rod does not occur upon tightening of the rodto the system.

FIGS. 1-13 depict non-limiting example embodiments of rod couplingdevices, systems and methods configured to increase surface area betweenthe locking cap or the screw head and the rod, and therefore decreaseplastic deformation of the rod. Such devices and systems may include forexample a saddle insert, an integrated locking cap, and/or a screw headhaving an incorporated saddle geometry.

The present embodiments allow pedicle screw systems to become compatiblewith the use of PEEK rods, increasing the versatility of the screwsystems. The present embodiments are advantageous e.g., in that theyaccommodate the use of various instrumentation used by surgeons. In someembodiments, the PEEK rod constructs described herein can be revised tobe formed at least in part by titanium as well as other biocompatiblematerials, such as stainless steel and alloys.

In example embodiments, rod coupler systems may include a coupling bodyhaving a bone fastener, such as a pedicle screw, disposed therethrough,and a saddle having a first side of the saddle abutting the bonefastener within the coupling body, and a second side of the saddleopposite the first side, having a concave portion configured to abut anelongate rod along at least two lines of contact between the saddle andthe rod.

FIGS. 1-3 depict non-limiting example embodiments of saddle insert rodcoupler systems in accordance with non-limiting example embodiments ofthe present invention. In particular, these embodiments depict a saddle2 having a concave surface that essentially corresponds to the diameterof an elongate rod 4, such as a PEEK rod, to be used. The saddle 2 canbe inserted e.g., into the bottom of a pedicle screw assembly. Thesaddle's shape 2 serves to increase the surface area contact between thetop of the saddle 2 (and therefore between the top of the screw head 6Aof a pedicle screw 6) and the bottom of the rod 4A. This increasedsurface area decreases the pressure on the rod when a set screw 8 (suchas a hexagonal set screw) is finally tightened, eliminating significantplastic deformation of the rod. The saddle insert 2 may be inserted intothe screw head with a slight press fit to maintain its positioning, andfeatures into the rod slot in the screw head to prevent axial rotation.According to example methods, the insert saddle 2 may be placed in theassembly before screw insertion into the pedicles of a patient.

FIG. 1 depicts a perspective view of the saddle 2 before insertion intoa pedicle screw assembly or system. As shown in FIG. 2, according toexample embodiments, a set screw 8 disposed in a cap 10 of a couplingbody 12, may be used to apply downward pressure on an elongate rod 4,disposed between the saddle 2 and the cap 10, to hold the rod 4 firmlyin position. The placement of a rod in the saddle 2 is depicted in FIG.3, (the end of the rod being depicted in this front view), prior to alocking cap and or set screw being placed thereover.

According to non-limiting example embodiments a coupling body mayinclude an inner surface portion at a lower end of the coupling body.The inner surface portion may be configured for example to receive orengage the fastener. The coupling body may further have at least twosidewalls that define two upwardly extending arms that define two slotscapable of receiving the elongate rod. The coupling body (e.g., element12 in FIG. 2) may be e.g., of a tulip shape for example, and may includea first and second opening in the sidewalls that are configured toreceive the elongate rod. As depicted for example in FIGS. 2 and 12. Thesaddle should be configured such that the concave portion aligns withthe slit of the coupling body, thus allowing the rod to fit within theconcave portion of the saddle while the saddle is within the couplingbody.

According to non-limiting example embodiments, a cap may engage with anupper end of the coupling body and capture an elongate rod within arecess of an inner surface portion of the elongate body. The cap may beconfigured so as to be capable of applying a downward force upon theelongate rod.

According to example embodiments, the coupling body may include at leastone groove disposed about an interior sidewall of the coupling body. Thecap may include at least one tongue configured to ride within the grooveof the coupling body. The cap may also include a lip that engages theupper end of the coupling body to align the tongue of the cap and thegroove of the coupling body when the cap is inserted into the couplingbody. According to alternative embodiments, the coupling body mayinclude at least one tongue and the cap may include at least one groove,wherein the tongue of the coupling body rides within the groove of thecap. These and various other methods and configurations for engaging acap with a coupling body may be within the skill of those in the art andall such embodiments are intended to be encompassed by the presentembodiments.

With reference to the figures as non-limiting examples, a locking cap 10may be provided that allows the user to easily insert the cap into thecoupling body 12. For example, with reference to FIG. 2, a cap 10 isprovided that may be placed within the coupling body 12. In theseexample embodiments, the cap 10 may generally match the shape ofcoupling body 12. The cap 10 is configured to fit substantially withinthe interior side walls of the coupling body 12. It should be understoodthat alternative designs and shapes may be used. A set screw 8 may bedisposed in the locking cap.

According to non-limiting example embodiments, rotation of the cap to asecond position relative to the coupling body presses an elongate rodagainst at least one saddle e.g., a saddle abutting said bone fastenerand/or a saddle adjacent to or otherwise configured with said cap, sothat the at least one saddle abuts said rod, and locks the coupling bodyand rod in position relative to one another and relative to the bonefastener.

The cap may include a locking element capable of securely holding theelongate rod in a fixed position relative to the coupling body. The capmay include a threaded opening and the locking element comprises athreaded set screw disposed within the threaded opening, wherein the setscrew is capable of applying downward pressure on the elongate rod tolock the elongate rod in position.

According to example embodiments, the cap and coupling body may beconfigured with at least one detent and corresponding recess thatcontact each other when the cap is in the second position to resistinadvertent loosening of the cap from the coupling body. Rotation of thecap toward to the second position may cause the detent and correspondingrecess to provide a tactile or audible signal to the physician, so aphysician is aware that the two are essentially locked with respect toone another.

In some embodiments, the cap may include a sidewall having a first andsecond channel formed therein, wherein the first and second channels arewider than the diameter of the elongate rod. The first and secondchannels may be configured to permit the cap to rotate from e.g., 5-90degrees or 20-40 degrees when in communication with the coupling bodywithout being impeded by the elongate rod. According to exampleembodiments, the cap may be configured to provide a tactile or audibleclick when rotated to the second position.

Bone fasteners according to the present invention may include any bonefastener known to those skilled in the art. According to non-limitingexample embodiments, the bone fastener may be a pedicle bone screwhaving a head. Non-limiting example screws may be made of any suitablematerial, including for example titanium. Example screws may also be ofany size and/or configuration known to those skilled in the art.Additionally, example screws may have various diameters, such assubstantially uniform diameters, or they may have two or more diametersor may be tapered.

Rod coupling systems provided herein may further include one or more ofa locking cap, a set screw disposed in the locking cap, and an elongaterod.

Also provided are devices that include a bone fastener and a saddleattached thereto, in which the saddle has a first side that abuts thebone fastener and a second side opposite said first side, which secondside has a concave portion that is configured to receive and support arod along at least two lines of contact between said saddle and saidrod.

According to non-limiting example embodiments, the concave portion ofthe saddle may be shaped so as to substantially correspond to a portionof surface area of the elongate rod. For example, as depicted in FIG. 3,according to non-limiting example embodiments, a surface portion of abottom of the rod may substantially correspond to the curvature of theconcave portion of the saddle, such that much of the correspondingsurface portion of the rod is in contact with the saddle and pressuremay be distributed over the areas in contact.

The saddle insert devices and systems increase contact through a step ofplacing the insert into the bottom of the screw head before it isinserted into the pedicle of a patient.

According to example embodiments, the saddle (e.g., either abutting thebone fastener or abutting or integrated with a locking cap), may have asmaller radius than the radius of an elongate rod to be insertedtherein.

Rods according to the present invention may be any suitable size inlength and/or diameter and may include for example a PEEK material, or acombination of PEEK and another ingredient. Non-limiting examples ofrods that may be used in accordance with the present invention mayinclude for example any rod configured for use with bone screws.

The rod may contain PEEK as a component thereof. According tonon-limiting example embodiments, at least part of the rod is made ofPEEK. Example rods may include for example titanium rods, rods thatinclude PEEK on the outside of the rod, for example in the form of atube, with titanium therein for example by a titanium rod of a desiredsize being inserted into the PEEK tube. Example rods may be of anysuitable shape or design for use in conjunction with bone screws. Theshape of example rods may be for example in a generally elongate shape.Further examples of rods that may be used in accordance with theinventions herein are provided herein below.

Further provided are methods that include inserting a saddle into acoupling body such that the saddle abuts a bone fastener in the couplingbody on a first side of the saddle, and wherein the saddle has a secondside opposite said first side, which second side has a concave portionthat is configured to abut a rod along at least two lines of contactbetween the saddle and said rod. The present methods may further includeinserting the bone fastener into a patient, adding an elongate rod tothe bone fastener such that the elongate rod abuts the saddle and addinga cap over the rod. The methods may further include securing the capand/or tightening the cap over the rod.

According to example embodiments of integrated locking caps, a rodcoupler system is provided which includes a coupling body having a bonefastener disposed therethrough, a locking cap adapted for attachment tothe coupling body, and a saddle having a first side of the saddleabutting the locking cap, and a second side of the saddle opposite thefirst side, the second side having a concave portion configured to abutan elongate rod along at least two lines of contact between the saddleand the elongate rod. Such example systems may further include a setscrew.

FIGS. 4-11 depict non-limiting examples of integrated locking capembodiments of the present invention. According to these exampleintegrated locking cap embodiments, the saddle 30 may be built into oradded to the cap 40 itself, prior to insertion into a patient, thuseliminating any potential extra steps in surgery.

According to non-limiting example embodiments, screw head design mayallow for the surface area contact on both sides of the rod to beincreased, thus reducing or eliminating plastic deformation.

According to the examples depicted in FIGS. 4-11, a saddle 30essentially matching the diameter of a PEEK rod 60 to be used, is fixed(possibly temporarily or removably fixed) to a modified locking cap 40.FIG. 4 depicts an exploded view of an integrated locking cap assembly.In particular, FIG. 4 depicts a cap 40, which is configured to beattachable to a saddle 30, and may have a set screw 50 disposed throughsaid cap. FIG. 5 depicts a perspective view of an assembled integratedlocking cap assembly having the components depicted in FIG. 4.

As depicted in FIGS. 6 and 7, the saddle features into the bottom of thecap such that the saddle axis is perpendicular to the locking cap wings.FIG. 6 depicts a cross sectional view of the integrated locking capassembly of FIG. 5, in which the saddle is not yet engaged with alocking cap. FIG. 7 depicts a cross sectional view of the integratedlocking cap assembly of FIG. 6, after the saddle has been turned e.g.,90 degrees to engage the saddle with the locking cap. By way of example,a 90 degree turn engages a ledge 32 on the top portion of the saddlewith a groove 44 in the locking cap, preventing separation of thecomponents. A CAM mechanism between the saddle and the cap resistsunwanted rotation, and thus temporarily fixes the two componentstogether. The saddle/cap assembly can then be inserted into the screwhead using a standard locking cap driver.

FIG. 8 depicts a perspective view of the integrated locking cap assemblyof FIG. 7, in which the saddle is engaged with the locking cap. FIG. 9depicts a perspective view of a pedicle screw 64 assembly having a rodinserted therein and the integrated locking cap assembly of FIG. 8 isinserted over the rod.

FIG. 10 depicts a perspective view of the pedicle screw assembly havinga rod inserted therein and the integrated locking cap assembly of FIG. 8inserted over the rod, after the cap has been rotated to lock the cap.In particular, a 90 degree turn engages the locking cap into the screwhead, captures the rod 60, and disengages the saddle 30. The saddle isthen clamped to the top of the rod by tightening the locking cap setscrew 50. As with the saddle in other embodiments herein, the saddle 30increases the surface area contact with the rod (in the case of theseembodiments, the surface area contact between the locking cap set screwand the top of the PEEK rod) when the set screw is tightened, thuseliminating or decreasing plastic deformation of the rod that mightotherwise occur.

FIG. 11 depicts a cross sectional front view of the assembly of FIG. 10in which the integrated locking cap depicted e.g., in FIG. 8 isconfigured in a pedicle screw assembly over an elongate rod.

Non-limiting example embodiments of the present invention are directedto rod coupler systems that include a coupling body having a bonefastener, such as a pedicle screw disposed therethrough. The couplingbody may have a locking cap inserted therein. Also included is a saddlehaving a first side, which abuts the cap within the coupling body. Thesaddle also has a second side opposite said first side, which secondside has a concave portion that is configured to receive and contact arod along at least two lines of contact between said saddle and saidrod. The concave portion of the saddle may be shaped so as tosubstantially correspond to a portion of surface area of the elongaterod. A set screw may be further provided in the locking cap.

The bone fastener may be a pedicle screw. Rod coupling systems providedherein may further include one or more of the elongate rod itself and aset screw disposed in the locking cap.

Also provided are integrated locking cap devices that include a lockingcap adapted for attachment to a coupling body and a saddle having afirst side, which abuts and is removably attached to the locking cap andhas a second side opposite said first side, which second side has aconcave portion that is configured to receive and contact a rod along atleast two lines of contact between said saddle and said rod. The devicesmay further include a set screw disposed in the locking cap.

Further provided are methods that include inserting a rod into acoupling body such that the rod abuts a bone fastener in the couplingbody, and adding a saddle over said rod, within the coupling body,wherein the saddle has a first side abutting a locking cap, a secondside opposite said first side, which second side has a concave portionthat is configured to abut said rod along at least two lines of contactbetween said saddle and said rod. The methods may further includesecuring the cap to the saddle, securing the cap to the coupling body,and/or tightening the cap over the rod. Also, it should be noted thataccording to example methods the saddle and or cap may be added to thecoupling body prior to inserting the rod there-between.

According to further example embodiments, the rod may be added to asystem that includes both an integrated locking cap (i.e., a saddleintegrated with the locking cap) and a saddle insert that abuts a bonefastener, such that saddles contact multiple sides of the rod.

Example embodiments of integrated locking caps build a saddle or saddleconfiguration into the cap itself, eliminating extra steps in surgery.

Further example embodiments include polyaxial screws or locking capshaving a concave portion configured to abut an elongate rod along atleast two lines of contact between the polyaxial screw and/or thelocking cap and the rod.

Examples of novel screw head embodiments are depicted in FIGS. 12-13,which allow for surface area contact on both sides of the rod to beincreased, eliminating possible plastic deformation of the rod. Theseembodiments feature e.g., a polyaxial screw tulip head 70 thatincorporates a saddle feature 90 into the surface in contact with a rodto be inserted therein (See FIG. 12). The saddle feature may beincorporated into the wedge, clamp, and/or tulip itself. The design maybe used in conjunction with an incorporated locking cap 94 that has asaddle type feature 80 (See FIG. 13). This design greatly increases thesurface area contact with the rod on top and bottom of the rod and willessentially eliminate plastic deformation of the rod upon finaltightening.

Thus, the present invention provides a polyaxial screw having a portionadapted for insertion into bone and a head having a concave portionconfigured to abut an elongate rod along at least two lines of contactbetween the polyaxial screw and the rod.

Further non-limiting example embodiments include specially designedinserts, locking caps and/or unique rod shapes, which will increase thesurface area contact with rods, particularly those made of PEEK, toreduce notching of the rods. Thus, according to non-limiting exampleembodiments, titanium screws (rod screws) may be used, even with rodsthat include PEEK.

By way of example, saddles are provided that include a first sideconfigured to be attached (e.g., detachably attached) to a bone fasteneror to a locking cap for a coupling body; and a second side opposite thefirst side of the saddle, the second side having a concave portionconfigured to abut an elongate rod along at least two lines of contactbetween the saddle and the elongate rod.

By way of non-limiting example embodiment, FIG. 14 depicts embodimentsin which a saddle insert 100 is provided, in which the saddle insert isconfigured to either abut the bone fastener or abut (or be integratedwith) a locking cap, on a first side of the saddle (bottom of the saddlein FIG. 14), and which has a concave portion on a second side of thesaddle (top of the saddle in FIG. 14). In these example embodiments, theconcave portion of the saddle may have a smaller radius 106 than theradius of an elongate rod 110 to be inserted therein. FIG. 14demonstrates that the undersized radius 102 creates two tangent lines ofcontact 104 between the saddle and the rod, rather than a single line ofcontact. The increased surface area of contact between the saddle andthe rod, decreases stress on the rod. Having little or no contactbetween the rod and the saddle at the center of the saddle 106,eliminates stress risers.

Thus, non-limiting embodiments of the present invention include a saddlehaving a first side and a second side, the first side being configuredto contact a screw or a cap, and the second side being configured with aconcave portion having a radius smaller than the radius of a rod to comeinto contact with at least two tangent lines of said saddle.

Further example embodiments may include a saddle (again either underand/or over the rod), which has a smaller radius than the radius of anelongate rod to be inserted therein, and which further includes one ormore dimples within the radius, such that there are three or more linesof contact between the elongate rod and the saddle, as depicted forexample in FIG. 23. In particular, FIG. 23 depicts front (A) and side(B) cross sectional views of a dimple interface of a saddle 200 with arod 206 in accordance with non-limiting example embodiments. In thedepicted embodiments a rod 206 contacts the saddle 200 at at least twolines of contact 202, which extends much of the length of saddle. Thedimple 204 also extends much of the length of the saddle as shown asreference numeral 212, in the cross sectional side view of FIG. 23B,having drop offs 214 on either side of the dimple. Contact is also madebetween the rod and the saddle at at least one dimple 204 in the saddle.The dimple eliminates sharp edge contact and reduces stress risers.

FIG. 15 depicts non-limiting example embodiments of an obrand rod whichmay be used in accordance with the present invention. In particular,FIG. 15 depicts a rod shape that may have e.g., two interlocking circlesconnected by flats 124 on either side. This configuration allows anultimately larger rod to fit in a screw system. 122 is the bottom of afirst, lower circle, 120 is the top of an upper circle. Larger A/Pdimensions are believed to increase strength, while still fitting in thescrew. Thus, combining the height of two circles is believed to beadvantageous. Accordingly, provided herein is an elongate rod configuredfor a rod coupler system, which includes two elongate curved sides andtwo elongate flat sides.

FIG. 16 depicts a non-limiting example embodiment of a composite rod 130that may be used in accordance with the present invention. In theseembodiments, a titanium rod 134 may be pressed into a tube 132 that ismade of PEEK. Optionally, additional materials such as stainless steel,alloys, PCU, and other biocompatible materials can also be pressed intothe tube 132. According to other example embodiments, the PEEK outerlayer may be added to the outside of the titanium rod. The inclusion oftitanium in the composite rod adds stiffness and strength to the PEEKmaterial forming part of the rod. Titanium allows the same strength in asmaller rod. Titanium also allows for visibility of the rod on an x-ray.

FIGS. 17 and 18 depict example PEEK rods that may be used in accordancewith the present invention, which offer various levels of stiffness.FIG. 17 in particular, depicts various examples of rods having differentamounts of titanium forming part of the rod. The rods range from a PEEKrod having no titanium therein 140 (least stiff) to a PEEK rod having asmall inside portion of titanium 142, to a PEEK rod having more titanium144 to a full titanium rod 146 (more stiff). This system offers variouslevels of stiffness for surgeon preference and possibly topping off atthe end of the rod, as depicted in FIG. 18. FIG. 18 shows for exampletwo rods 148 and 150, corresponding roughly to the rods 142 and 144 fromFIG. 17, having PEEK portions topping off the rods to add variablestiffness. The stiffness of various rods provided herein, is afforded bytitanium rods of various diameters molded within or wrapped around PEEK.

This provided herein are elongate rods configured for a rod couplersystem, in which the rod is a composite rod having a first inner portionof titanium and a second outer portion that includes PEEK.

FIG. 19 depicts examples of barreled rods 160 in accordance withnon-limiting example embodiments. In particular, FIG. 19 depicts exampleconfigurations of rods that may be used to increase the diameter A ofthe rod when it sits in pedicle screws, according to example embodimentsprovided herein. In particular, barrels 162 are provided near one orboth ends of a rod 164. According to non-limiting examples, suchbarreled rods may be of different lengths B, and may be made ofdifferent materials. For example, barreled rods may include titanium orPEEK or some combination thereof (e.g., composite embodiments asdescribed herein). The barreled rods allow for flexibility whilestrengthening a rod/screw interface.

FIG. 20 depicts a posted screw system that may be used in accordancewith non-limiting example embodiments. In particular, FIG. 20 depicts aposted screw system 170 that may be used with a stabilization system.The posted screw system provides a system and method for attaching a rodto a screw using a collet. In particular, the collet 174 may be used tolock a rod 176 to a screw 172. In some embodiments, the collet isprovided around a rod and then the screw is inserted through openings inthe collet. When the screw is tightened, the collet also tightens aroundthe rod by circumferential pressure. Such systems have a larger surfacearea contact than other systems. Additionally, such systems provideequal force all around the rod, so there is little or no deformation ofthe rod. Tightening the screw forces the collet to lock onto the rod.

Thus, example systems may include a screw that passes through at leasttwo portions of a collet, and optionally a rod passing therethrough aswell.

Also included are methods of fixing a rod which include passing a rodthrough a collet and tightening a screw that passes through two or moreholes of the collet.

FIG. 21 depicts a different collet system that may be used in accordancewith the non-limiting example embodiments, for example with a spinalstabilization system. In these embodiments a rod is inserted into acollet. Tightening a set screw 182/184 compresses the collet 180 to lockthe rod 186. As with other embodiments, devices, systems and methods ofthese embodiments, may include any number of different kinds of screwsand/or rods

FIG. 22 depicts a cross sectional view of an example rod having flatsthat may be used in accordance with the present invention. FIG. 22depicts for example a rod 190 that has a cross sectional configurationthat is relatively flat on each of two sides 192 and may be curved ontwo sides 194 that extend in an anterior-posterior direction. In suchembodiments, a set screw may lock on to the flat side and thereforeincrease surface area contact.

Also provided are integrated locking caps that include a locking capadapted for attachment to a coupling body, and a saddle having a firstside of said saddle removably attached to the locking cap, and a secondside of the saddle opposite the first side, the second side having aconcave portion configured to receive and abut an elongate rod along atleast two lines of contact between the saddle and the elongate rod.

FIGS. 24-29 depict further examples of integrated locking capembodiments. In particular, they involve a specially designed insert andlocking cap which will increase the surface area contact with the PEEKrods to reduce notching of the rod.

FIGS. 24-29 feature a saddle insert 310 with two grooves 312, 314oriented at 90 degrees from each other, an initial insertion groove 312and a rod interface groove 314. Both grooves have a diameter matchingthat of the rod, such as a PEEK rod. In other embodiments, one groovewill have a slightly oversized diameter and one groove will have aslightly undersized diameter. In some embodiments, the rod interfacegroove 314 can be undersized to advantageously provide at least twolines of contact. The saddle insert features into the bottom of amodified locking cap 320. The insert interfaces with a channel cut intothe locking cap to couple the saddle with the cap rotationally whilestill allowing it to translate axially to capture the rod. Axialmovement is to be controlled by the locking cap set screw.Advantageously, the locking cap 320 and saddle insert 310 are connectedtogether such that they will rotate with each other. In someembodiments, the saddle insert includes a tongue feature (shown in FIG.24) that mates with a groove in the locking cap 320 to secure the twocomponents together.

FIG. 24 depicts an exploded view of an integrated saddle-locking capdesign. In FIG. 24, the saddle insert 310 is depicted with multiplegrooves 312 and 314. The locking cap 320 is depicted separated from thesaddle. Devices and systems may include the saddle insert and lockingcap already attached to one another, or separated, such that they may belater attached.

According to example embodiments, the saddle insert 310 snaps onto thebottom of the set screw locking it onto the screw while still allowingit to rotate independently of the screw. The saddle screw assembly isloaded into the modified locking cap such that the saddle tongue slidesinto the mating groove on the cap. This fixes the caps movementrotationally with the locking cap while still allowing axial movement.

This cap can be inserted and locked using a standard locking cap driver.A ninety degree turn engages the locking cap 320 with the screw head,captures the rod, and aligns the rod interface groove with the rod. Thesaddle is then clamped into place by tightening the locking cap setscrew. The saddle moves axially with regards to the cap but rotatesfreely with regard to the set screw. In some embodiments, the saddle 310will move in upward and downward translation relative to the locking cap320. Advantageously, the saddle increases the surface area contactbetween the locking cap set screw 340 and the top of the rod. Thisincreased surface area decreases the pressure on the PEEK rod when theset screw 340 is final tightened, eliminating significant plasticdeformation.

FIG. 25 depicts a side view of an integrated saddle-locking cap designfully assembled.

FIG. 26 depicts a cross-section view of fully assembled saddle-lockingcap design showing tongue and groove attachment. In particular, thefigure shows how the saddle attaches to the set screw through thelocking cap with a cross-sectional front view of a rod 330 depicted.

FIG. 27 depicts a saddle-locking cap design inserted into standard screwhead. FIG. 28 depicts a saddle-locking cap design rotated 90 degreesfrom its position in FIG. 27 (as can be seen e.g., by the saddle 310configuration in each figure) and locked into place.

FIG. 29 depicts the integrated locking cap of FIGS. 27 and 28, which hasbeen inserted into a standard screw head, and which has been locked intoplace as in FIG. 28 and further having had the set screw tightened andthe saddle advanced locking the rod.

A method of inserting and using the rod coupler system will now bedescribed with respect to FIGS. 28 and 29. After a rod 330 has beeninserted into a coupling body, the integrated locking cap 320 and saddle310 (e.g., coupled by a tongue-and-groove feature) can be provided. Thelocking cap 320 includes a bore for receiving a set screw 340therethrough. Once the integrated locking cap 320 and saddle 310 aredeposited in the coupling body, the locking cap 320 and saddle 310 canbe rotated (e.g., about 90 degrees) within the coupling body. Thisadvantageously secures the integrated locking cap 320 and saddle 310 tothe coupling body and desirably orients the bottom of the saddle 310such that the saddle opening aligns with the rod member 330.

With respect to FIG. 29, once the integrated locking cap 320 and saddle310 are properly oriented within the coupling body, the set screw 340can be downwardly threaded using a screwdriver. As the set screw 340 isdownwardly threaded through the bore in the locking cap 320, the distalend of the set screw 340 pushes down on the surface of the saddle 310,which also translates downward onto the rod member 330. The saddle 310thus compresses the rod member 330, thereby securing the rod member 330in the coupling body, as shown in FIG. 29.

Advantages of the devices depicted in FIGS. 24-29 include that thedevices increase the surface area contact between the locking cap andthe screw head, and the PEEK rod, which decreases the amount of plasticdeformation in the rod. This allows stabilization systems for example,to become compatible with the use of PEEK rods or other rods describedherein, increasing the versatility of both systems. These embodimentsare advantageous in the use of instrumentation that is familiar to boththe surgeon and the sales force. The use of any of the rods set forthherein is contemplated with regard to these embodiments, including e.g.,rods having PEEK, rods of titanium and rods that include combinations ofboth materials, such as the composite rods discussed herein. Alsocontemplated are potentially differently shaped rods as discussedherein, so long as the saddle is configured to accommodate the rod shapeor vice versa.

The integrated locking cap builds the saddle into the cap itself,eliminating any extra steps in surgery. Fixing the saddle insert ontothe set screw allows for easy revision as loosening the set screw andremoving the locking cap removes the saddle at the same time withoutrequiring extra instrumentation or additional steps.

Other example embodiments include kits that include one or morecomponents of the present devices and systems. For example, kits mayinclude at least one coupling body having a bone fastener disposedtherethrough, and a saddle. The saddle has a first side, which isconfigured so as to abut the bone fastener within the coupling body anda second side of the saddle opposite the first side, the second sidehaving a concave portion configured to receive and support a rod alongat least two lines of contact between the saddle and the rod. These kitsmay also include on or more of the following components: a locking cap,a set screw, a rod, a tool for assembling a rod coupler system orportions thereof, a tool for inserting a rod coupler system into apatient, a tool for tightening a set screw so as to secure a rod withina rod coupler system assembled using the kit components; and/orinstructions for use and/or assembly of a rod coupler system providedherein.

According to example embodiments, at least two components of the kit maybe preassembled together within the kit. For example, within a kit abone fastener and saddle may be provided already assembled within acoupling body, and one or more additional components such as a lockingcap and/or elongate rod may optionally be separately provided within thekit. Alternatively, individual components may be provided that may beput together for example by a technician or physician.

All or parts of the present systems may come pre-assembled, for examplewith the screw and saddle already being pre-inserted into the couplingbody, or the parts may be provided separately for example in the form ofa kit, and assembled by a technician or surgeon.

Thus, the cap system may include a locking cap configured to fit atleast partially within a locking body; and a saddle abutting saidlocking cap, said saddle having a concave portion that substantiallycorresponds to a portion of surface area of the rod, and beingconfigured to accept the rod therein. Example systems may furtherinclude one or more of the following: cap or a set screw disposed insaid cap, and the rod itself. All or parts of the system may comepre-assembled, for example with the screw and saddle already beingpre-inserted into the coupling body, or the parts may be individual, forexample in the form of a kit, for being put together. Example kits mayprovide further information or directions regarding assembly. Furtherprovided herein are methods of assembling the rod coupler systemsprovided herein, and methods of using the present rod couplers thatinclude inserting the couplers into a patient.

Also provided are kits that include a locking cap adapted for a couplingbody and a saddle having a first side, adapted to abut and attach to thelocking cap and a second side opposite said first side, which secondside has a concave portion that is configured to receive and contact arod along at least two lines of contact between said saddle and saidrod. In the kits, the locking cap and the saddle may be pre-attached toone another (e.g., removably attached to one another), or they may beseparately provided. The kits may further include a set screw.

Provided kits may also include a coupling body having a bone fastener,such as a pedicle screw. Further examples of kits according to thepresent invention may include one or more additional components such asa rod, a tool for assembling the present systems or portions thereof, atool for inserting the present devices or systems into a patient, a toolfor tightening a set screw so as to secure a rod within the presentsystems assembled using the kit components; and instructions for use orassembly of systems comprising the kit components.

According to non-limiting example embodiments, at least two componentsmay be preassembled together within the kit.

The present invention may include methods of assembling the present rodcoupler systems. According to non-limiting example embodiments, portionsof the assembly may take place outside a patient, while other portionsof the assembly may be performed by a surgeon during the process ofinserting the assembly into a patient. For example, in non-limitingexample embodiments, a saddle as provided herein insert may increase thesurface area contact through a step of placing the saddle/insert intothe bottom of the screw head before the saddle/screw assembly isinserted into the pedicle of a patient.

Methods may also include methods of treating a patient in need thereof,which include inserting one or more of the present systems or devicesinto a patient to provide support to a portion of the body of thepatient. For example, in some embodiments, the devices and methodsdescribed herein are configured to provide support to a spine or back ofa patient. In other embodiments, other portions of the body of thepatient are supported by the devices.

While certain features of the described implementations have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the scope of theembodiments.

What is claimed is:
 1. A rod coupler system comprising: a coupling bodyhaving a bone fastener disposed therethrough, and a saddle having afirst side of said saddle abutting said bone fastener within saidcoupling body, and a second side of said saddle opposite said firstside, said second side having a concave portion configured to abut anelongate rod along at least two lines of contact between said saddle andsaid elongate rod.
 2. The rod coupler system of claim 1, wherein saidconcave portion of said saddle is shaped so as to substantiallycorrespond to a portion of surface area of the elongate rod.
 3. The rodcoupler system of claim 1, further comprising at least one additionalcomponent selected from the group consisting of a locking cap, a setscrew disposed in said locking cap, and the elongate rod.
 4. The rodcoupler system of claim 1, wherein said bone fastener comprises apedicle screw.
 5. The rod coupler system of claim 1, further comprisingat least one additional component selected from the group consisting ofa locking cap, a set screw, a rod, a tool for assembling the rod couplersystem or portions thereof, a tool for inserting the rod coupler systeminto a patient, and a tool for tightening a set screw so as to secure arod within the rod coupler system.
 6. The rod coupler system of claim 1,wherein the elongate rod is formed of PEEK.
 7. The rod coupler system ofclaim 1, wherein the elongate rod is a composite rod formed of at leasttwo materials, one being PEEK.
 8. A coupling system comprising: a saddlecomprising: a first side configured to be detachably attached to a bonefastener or to a locking cap for a coupling body; and a second sideopposite said first side of said saddle, said second side having aconcave portion configured to abut an elongate rod along at least twolines of contact between said saddle and said elongate rod.
 9. Thesystem of claim 8, wherein the saddle radius is configured to be asmaller radius than a radius of the elongate rod.
 10. The system ofclaim 9, wherein the saddle further comprises at least one dimple withinthe radius, which is configured to also make contact with said elongaterod, such that said saddle is configured to abut said rod along at leastthree lines of contact.
 11. The system of claim 8, further comprising acap attached to the saddle, wherein the saddle is rotated independentlyfrom the cap.
 12. The system of claim 8, further comprising a capattached to the saddle, wherein the saddle is rotated when the cap isrotated.
 13. A rod coupler system comprising: a coupling body having abone fastener disposed therethrough, a locking cap adapted forattachment to said coupling body, and a saddle having a first side ofsaid saddle abutting said locking cap, and a second side of said saddleopposite said first side, said second side having a concave portionconfigured to abut an elongate rod along at least two lines of contactbetween said saddle and said elongate rod.
 14. The rod coupler system ofclaim 13, wherein said concave portion of said saddle is shaped so as tocorrespond to a portion of surface area of the elongate rod.
 15. The rodcoupler system of claim 13, further comprising at least one additionalelement selected from the group consisting of the rod and a set screwdisposed in said locking cap.
 16. The rod coupler system of claim 13,wherein said bone fastener comprises a pedicle screw.
 17. The rodcoupler system of claim 13, wherein the elongate rod is formed of PEEK.18. The rod coupler system of claim 13, wherein the elongate rodcomprises a titanium rod pressed into a PEEK tube.